Label night-session products and hide day-only symbols at night.

Mark tradable varieties with a night tag; during 21:00-02:30 filter out index futures and other products without night sessions from symbol picker and recommend list.

Co-authored-by: Cursor <cursoragent@cursor.com>

market_sessions.py

@@ -45,6 +45,19 @@ def is_trading_session(now: Optional[datetime] = None) -> bool:
     return False
 
 
+def is_night_trading_session(now: Optional[datetime] = None) -> bool:
+    """当前是否处于夜盘时段（21:00–02:30，且整体仍在交易时段内）。"""
+    if not is_trading_session(now):
+        return False
+    d = now or datetime.now(TZ)
+    if d.tzinfo is None:
+        d = d.replace(tzinfo=TZ)
+    else:
+        d = d.astimezone(TZ)
+    t = d.hour * 60 + d.minute
+    return t >= 21 * 60 or t < 2 * 60 + 30
+
+
 def _session_open_allowed(day: datetime, hour: int, minute: int) -> bool:
     wd = day.weekday()
     if (hour, minute) == (9, 0) or (hour, minute) == (13, 30):